One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (“ABS”) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track.
The methods for positioning the transducers can generally be grouped into two categories. Disc drives with linear actuators move the transducer linearly generally along a radial line to position the transducers over the various tracks on the information storage disc. Disc drives also have rotary actuators which are mounted to the base of the disc drive for arcuate movement of the transducers across the tracks of the information storage disc. Rotary actuators position transducers by rotationally moving them to a specified location on an information recording disc. A rotary actuator positions the transducer quickly and precisely.
The actuator is rotatably attached to a shaft via a bearing cartridge which generally includes one or more sets of ball bearings. The shaft is attached to the base and may be attached to the top cover of the disc drive. A yoke is attached to the actuator and is positioned at one end of the actuator. The voice coil is attached to the yoke at one end of the rotary actuator. The voice coil is part of a voice coil motor which is used to rotate the actuator and the attached transducer or transducers. A set of permanent magnets is attached to the base and cover of the disc drive. The voice coil motor which drives the rotary actuator comprises the voice coil and the permanent magnet. The voice coil is attached to the rotary actuator and the permanent magnet is fixed on the base. A top plate and a bottom plate are generally used to attach the set of permanent magnets of the voice coil motor to the base. The top plate and the bottom plate also direct the flux of the set of permanent magnets. Since the voice coil sandwiched between the set of permanent magnets and top plate and bottom plate which produces a magnetic field, electricity can be applied to the voice coil to drive it so as to position the transducers at a target track.
One problem associated with disc drives is that the actuator assembly may resonate or vibrate at certain frequencies which in turn causes the transducer within the slider to move off-track. In other words, if there is even a slight vibration, the slider may move away from the center of a track during a track following operation. If the vibration is too large, the transducer continuously crosses the track to be followed and little if any information can be read. Writing can not be accomplished since there is a risk, at these times, that the transducer may be positioned over another adjacent track and attempting to write may result in overwriting other data that is necessary. The source of vibration may be the natural resonance of an actuator assembly or may be due to other influences. One of these influences is airflow generated by the rotating discs. The airflow generated by the rotating disc or discs (also referred to as windage) excites head suspensions which in turn cause the slider and transducers to vibrate. The vibration causes run-out which is off-track motion. Of course as the density of tracks is increased, run-out due to smaller vibrations becomes more critical.
What is needed is a disc drive that reduces vibration of the suspension and attached transducer and slider resulting from airflow between the spinning discs in a disc drive. What is also needed is a disc drive in which there is less off-track motion or run-out. There is a constant need for a disc drive which has additional capacity as well as increased reliability without an appreciable rise in the error rate. There is also a need for methods and apparatus to reduce vibrations in the suspension and attached slider and transducer.